Field of the Invention
The present invention relates to a novel structure for a saw blade in such type that the saw blade is mounted and fixed to a drive source, which source performs a reciprocating circular motion (movement) with a small extent of swing amplitude (rotation angle), in order to make cutting.
The terminology “the arcuate swing” referred to hereunder in the specification signifies the aforementioned “reciprocating circular motion with a small extent of swing amplitude (rotation angle)”.
Prior Art
A saw blade is generally categorized in either a type of operation with a reciprocation movement (typically of a manually operable saw) or a type of circular movement (as a round saw). Both types of saw have high ability of cutting but do not yet become an ideal tool since they are problematic in safety, scatter loose particles from cutting, make loud noises, and so on.
Meanwhile, a specific electric cutting tool has been proposed as follows.
In detail, as shown in FIG. 6, a saw blade B exclusively used in the electric cutting tool is mounted and fixed, by use of a tightening screw, to a drive shaft A set in the body of the electric cutting tool. (The tool exemplified in FIG. 6 may mount, for example, a polishing member in place of the saw blade to thereby also serve as an electric file (rasp) or polisher.)
The drive shaft A does not make a unidirectional rotation but has a swing style of performing a reciprocating arcuate movement (arcuate swing) of a quite small swing angle (generally about 3.0 degrees). The tool is activated to cause the whole of the exclusive saw blade B to reciprocate at a small central angle. Strictly speaking, the cutting teeth on the saw blade make a circular movement, but show a spurious situation of linear reciprocating movement due to the quite small swing angle. And practically, due to the quite small swing amplitude, users who holding the tool in swinging may feel swing as of a swing type electric razor but is not impressed with as that the blade reciprocates transversely.
The cutting operation using the tool is carried out merely by straightly pushing the saw blade against wood to form a “slit hole” in the wood. For example, a saw blade disclosed in Japanese Unexamined Patent Application Publication No. 2000-512561 official gazette has basically the same structure as the exclusive saw blade B.
Naturally, it is possible to make a slit hole in the wood by use of a conventional hand-held saw with a round blade. However, this cutting is performed through unidirectional rotation of the blade. Thus, the blade basically tends to roll along on the wood to be worked. In detail, the cutting operation is carried out by first making a narrow through bore against the blade's force of rolling along on the wood, and then making larger the width of the through bore to a predetermined size. For this, it is naturally necessary to learn a specific working technique, which unlike the operation using the tool shown in FIG. 6 for which operation it is enough to merely push the tool's blade straightly against the wood in the direction of the wood's thickness. Besides, in use of the round saw, the loose particles from cutting jet and scatter at a substantial high initial rate from the slit bore being worked, thereby having a problem of deteriorating the working circumstances. This can be said to have various problems, such as high dangerousness and so on.
The mentioned problems can be cleared by use of the method making use of “the arcuate swinging of blade” for performing cutting. When the exclusive saw blade B is used for cutting, cutting can be carried out without troubles at the beginning of operation or when cutting a thin wood. However, there will be inconvenience when making a slit hole in a thick wood. In detail, there is such danger that the saw blade's left side end and right side end continue to collide against left and right lateral sides of the slit hole in the wood to thereby be heated and finally smoke, or, the cutting teeth on the ends of the saw blade are deformed due to heating. Such troubles have been confirmed actually.
Regarding reasons of happening of the above-mentioned facts which reasons will be detailed later, it is so inferred that as the cutting operation proceeds, the saw blade collides against the left and right sidewalls of the slit hole. Practically, there has been neither brought onto the market nor proposed any attempts of an improved saw blade structure having no above-mentioned troubles or proposing any improvement for them although generation of heat and deformation was known and seen as a problem.